1. Field of the Invention
The present invention relates generally to a reversing clutch mechanism for transmissions, and more particularly to a reversing clutch mechanism for marine transmissions of the type of having a pair of continuously driven friction clutches freely rotatably disposed on an output shaft and an intermediate clutch element axially moveable along the output shaft into selective frictional engagement with one or the other of the clutch members to rotate the output shaft in either a forward or reverse rotational direction.
2. Description of Prior Art
Reversing clutch mechanisms are commonly used in marine transmissions to selectively couple an engines drive shaft and a prop shaft to rotate the prop shaft in either a forward or reverse rotatational direction. A propeller is mounted to the free end of a prop shaft to propel the vessel in either a forward or reverse direction. These types of clutch mechanisms typically comprise a pair of oppositely driven clutches freely rotatably disposed on an output shaft coupled to the prop shaft. A coupling element is helically splined on the output shaft between the friction clutches and is moveable therealong toward and away from each friction clutch. The coupling element is provided with frictional engaging surfaces for engaging one or other of the friction clutches to rotate the prop shaft in either the forward or reverse rotational direction. At the moment the coupling element engages one of the clutches, the rotation of the propeller in the water transmits a torque to the prop shaft (and thus the output shaft). As a result, the output shaft attempts to rotate relative to the engaged coupling element causing the coupling element to be further urged into engagement with the clutch due to the helical spline connection between the output shaft and the coupling element. As the rotational speed of the prop shaft is increased, the torque transmitted to the shaft is also increased thereby urging the coupling element into tighter engagement with the friction clutch. Although this type of clutch mechanism has the advantage of virtually eliminating any possibility of clutch slippage because of the extremely tight engagement between the coupling element and the friction clutch, it also has the inherent disadvantage of being extremely difficult to disengage. That is, in addition to having to overcome the force of frictional engagement, the torque force transmitted through the prop shaft must also be overcome in order achieve disengagement. Of course, decreasing the rotational speed of the prop shaft prior to attempting disengagement helps, but a certain amount of torque always remains to be overcome before disengagement can be achieved.
Once solution to this problem is disclosed in the U.S. Pat. Number 3,269,497 to Bergstedt, issued Aug. 30, 1966. In this reverse clutch mechanism, the rotational power of the vessel's engine is utilized to achieve disengagement. Specifically, the coupling element is provided with a peripheral eccentric V-groove having side walls which axially reciprocate with rotation of the coupling element. A spring biased, wedge-shaped sliding pin extends into the groove and is moveable toward the side walls for engagement therewith. When the pin is urged against a side wall of the groove, the reciprocating camming action of the side wall against the pin urges the coupling element out of engagement with the friction clutch and into a neutral condition. However, with this system, the sliding pin has a tendency to get wedged or caught up in the groove. More particularly, the wedge-shaped sliding pin is forced down into the groove and into contact with the side walls by means of a spring and follows the eccentricity of the groove when the coupling element is engaged and rotating. This condition enables the sliding pin to stick or become wedged between the rotating side walls of the groove resulting in poor performance and likely damage to the clutch assembly.